February 23, 2019, 10:30:55 pm

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#### aspiringantelope

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##### Re: VCE Methods Question Thread!
« Reply #17685 on: February 11, 2019, 09:06:56 pm »
0
Hey, just a question -
Find the angle, correct to two decimal places, that the lines joining the given points make with the positive direction of the x-axis: $\left(c,b\right)\ and\ \left(b,c\right)$
I know how to do it when there are numbers and when it is positive but this just does not make sense?
Can someone help? I'm up to =
$\tan\theta=\frac{c-b}{b-c}$
I'm not sure what to do next if anyone can help me? Thanks!
Modified this because I was just going to skip the question until I came to something more weird??
Find the gradient of a straight line which is:
a) inclined at an angle of 120 degrees to the positive direction of the x-axis (first quadrant)
I wrote one question because I wanted to try the rest of them
« Last Edit: February 11, 2019, 09:10:51 pm by aspiringantelope »
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#### lzxnl

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##### Re: VCE Methods Question Thread!
« Reply #17686 on: February 11, 2019, 09:13:31 pm »
+1
Hey, just a question -
Find the angle, correct to two decimal places, that the lines joining the given points make with the positive direction of the x-axis: $\left(c,b\right)\ and\ \left(b,c\right)$
I know how to do it when there are numbers and when it is positive but this just does not make sense?
Can someone help? I'm up to =
$\tan\theta=\frac{c-b}{b-c}$
I'm not sure what to do next if anyone can help me? Thanks!
Modified this because I was just going to skip the question until I came to something more weird??
Find the gradient of a straight line which is:
a) inclined at an angle of 120 degrees to the positive direction of the x-axis (first quadrant)
I wrote one question because I wanted to try the rest of them

Are you aware that $\frac{c-b}{b-c} = -1$?

For the next one, use the fact that $m = \tan(\theta)$.
« Last Edit: February 11, 2019, 09:26:02 pm by lzxnl »
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#### darkz

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##### Re: VCE Methods Question Thread!
« Reply #17687 on: February 11, 2019, 09:15:14 pm »
+1
Hey, just a question -
Find the angle, correct to two decimal places, that the lines joining the given points make with the positive direction of the x-axis: $\left(c,b\right)\ and\ \left(b,c\right)$
I know how to do it when there are numbers and when it is positive but this just does not make sense?
Can someone help? I'm up to =
$\tan\theta=\frac{c-b}{b-c}$
I'm not sure what to do next if anyone can help me? Thanks!

\begin{aligned} \tan(\theta)&=\frac{c-b}{b-c}\\ &=\frac{-(b-c)}{b-c}\\ &=-1\\ \text{ }\\ \therefore \theta&=\tan^{-1}(-1)\\ &=\frac{-\pi}{4}\\ &\approx -0.79^c\\ \end{aligned}\\
« Last Edit: February 11, 2019, 09:17:12 pm by darkz »
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#### aspiringantelope

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##### Re: VCE Methods Question Thread!
« Reply #17688 on: February 11, 2019, 09:16:22 pm »
0
Are you aware that $\frac{b-c}{c-b} = -1$?

For the next one, use the fact that $m = \tan(\theta)$.
Wait is there a formula for that to be -1? Or did you just try random numbers? How did you work that out?
If so
-1 = $\tan(\theta)$
I'm also unsure what this turns to now >.< cause I'm not familiar with rearranging trig functions
WAIT SORRY
I know now cause it was just the wrong way around so i didnt understand at that point
Modification
$\tan\theta=-1$
$\tan^{-1}\left(-1\right)=\theta$
= -45

Had a look at and the answer was 135 degrees, is that supposed to be correct cause 180-45 = 135 but i'm not sure if there is such a formula
« Last Edit: February 11, 2019, 09:20:22 pm by aspiringantelope »
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#### darkz

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##### Re: VCE Methods Question Thread!
« Reply #17689 on: February 11, 2019, 09:27:59 pm »
+1
Wait is there a formula for that to be -1? Or did you just try random numbers? How did you work that out?
If so
-1 = $\tan(\theta)$
I'm also unsure what this turns to now >.< cause I'm not familiar with rearranging trig functions
WAIT SORRY
I know now cause it was just the wrong way around so i didnt understand at that point
Modification
$\tan\theta=-1$
$\tan^{-1}\left(-1\right)=\theta$
= -45

Had a look at and the answer was 135 degrees, is that supposed to be correct cause 180-45 = 135 but i'm not sure if there is such a formula

Well I never really fully understood these questions haha, but then I'd just assume that they they're looking for a positive answer. So then yeh, that'd be 135 (Refer to the attached diagram)

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#### aspiringantelope

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##### Re: VCE Methods Question Thread!
« Reply #17690 on: February 11, 2019, 09:32:29 pm »
0
Well I never really fully understood these questions haha, but then I'd just assume that they they're looking for a positive answer. So then yeh, that'd be 135 (Refer to the attached diagram)
Ok thanks! Just wondering where did the -(b-c)/b-c (I thought it was c-b/b-c as well o.O) (not b-c/b-c) (-) negative sign come from? the one in front of b-c on the numerator.
Thanks
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#### MB_

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##### Re: VCE Methods Question Thread!
« Reply #17691 on: February 11, 2019, 09:37:13 pm »
+1
Ok thanks! Just wondering where did the -(b-c)/b-c (I thought it was c-b/b-c as well o.O) (not b-c/b-c) (-) negative sign come from? the one in front of b-c on the numerator.
Thanks
-(b-c) is equal to c-b it's just writing it as -b+c and taking out -1 to get -(b-c)
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#### aspiringantelope

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##### Re: VCE Methods Question Thread!
« Reply #17692 on: February 11, 2019, 09:49:42 pm »
0
-(b-c) is equal to c-b it's just writing it as -b+c and taking out -1 to get -(b-c)

Where did the -1 come from o.O?
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#### darkz

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##### Re: VCE Methods Question Thread!
« Reply #17693 on: February 11, 2019, 09:52:54 pm »
+1
Where did the -1 come from o.O?

You factor it out, its just like
$2(x+2)=2x+4$

$-(a+b)=-a-b$

$-1\times a + -1\times b = -1(a+b)$
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#### EllingtonFeint

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##### Re: VCE Methods Question Thread!
« Reply #17694 on: February 12, 2019, 02:52:06 am »
0
Hello.
How do you get your Ti-nspire Cx Cas calculator out of Set-to-test mode?!!
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#### C14M8S

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##### Re: VCE Methods Question Thread!
« Reply #17695 on: February 12, 2019, 09:14:21 am »
0
Hey guys, I've got two questions -
1) Is it possible to map transformations from a matrix onto a function using the TI-nspire?
2) How would I work through the questions that I've attached? I understand how matrix transformations work, but I'm struggling to work through mapping inverse functions.
Cheers!
« Last Edit: February 12, 2019, 09:42:07 am by C14M8S »
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#### S_R_K

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##### Re: VCE Methods Question Thread!
« Reply #17696 on: February 12, 2019, 12:02:32 pm »
+1
Hello.
How do you get your Ti-nspire Cx Cas calculator out of Set-to-test mode?!!

You'll need to connect it to a computer with the Ti-nSpire CAS software, and there's an option to exit press-to-test mode. Ask your teacher.

Hey guys, I've got two questions -
1) Is it possible to map transformations from a matrix onto a function using the TI-nspire?

Yes, but i think it's probably more trouble than its worth.

Quote
2) How would I work through the questions that I've attached? I understand how matrix transformations work, but I'm struggling to work through mapping inverse functions.
Cheers!

For the first one (the second one is pretty much the same), find x' and y' by multiplying that 2x2 matrix by [x y] (as a column matrix, of course). That will give x' = 3y and y' = –2x. Then solve for y in terms of x', x in terms of y', and substitute into the original equation to get (x'/3) = 2(-y'/2) + 3. Rearrange to y = mx + c form.

#### C14M8S

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##### Re: VCE Methods Question Thread!
« Reply #17697 on: February 12, 2019, 04:22:56 pm »
0
Hey again,

How would I use the chain rule to differentiate the following? I couldn't really see how it ties into the problem, when I took g'(x) I got a result of 1/tan(x) and then simplified g'(pi/4) to 1/1 = 1, but the examiner's report says otherwise. Could someone please point out why I'm wrong?

« Last Edit: February 12, 2019, 05:18:57 pm by C14M8S »
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#### Sine

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##### Re: VCE Methods Question Thread!
« Reply #17698 on: February 12, 2019, 05:15:09 pm »
0
Hey again,

How would I use the chain rule to differentiate the following? I couldn't really see how it ties into the problem, when I took g'(x) I got a result of 1/tan(x) and then simplified g'(pi/4) to 1/1 = 1, but the examiner's report says otherwise. Could someone please point out why I'm wrong?

have you attached the right question? It seems to not be relevant.

#### C14M8S

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##### Re: VCE Methods Question Thread!
« Reply #17699 on: February 12, 2019, 05:20:19 pm »
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have you attached the right question? It seems to not be relevant.
Thanks for pointing that out - I've attached the correct question now >.<
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